Abstract

A method is presented that can be applied to phase-step interferometry to locate the regions within which integral multiples of π should be added to the wrapped phase that results from arctangent calculations. Unlike previous methods, this one is immune to the noise-related errors that confuse simple phase-unwrap schemes. It makes use of the fact that the noise-related errors occur at fixed locations in the phase map, whereas the location of the wrap regions depends on the way in which the arctangent is calculated.

Figures (3)

(a) Plot of half the difference of the values in the upper and lower plots in Fig. 1 (dashed line). The solid line plots these values converted to a staircase function for unwrapping, (b) Plot of the average of the values in the upper and lower plots in Fig. 1 (dashed line). The solid line plots the unwrapped phase values obtained by adding the staircase function from Fig. 2(a). Note that the transition greater than π between the third and fourth points has been preserved.

Two-dimensional array of phase-wrap regions calculated by subtracting phase values calculated with Eqs. (2a) and (2c) and dividing by 2. The filled circles indicate values of π/2, the open circles −π/2.